This application relates to hydrocracking processes with catalysts comprising MCM-36. MCM-36 is a layered material, having layers which are spaced apart by a pillaring agent. MCM-36 has a characteristic X-ray diffraction pattern.
Many layered material are known which have three-dimensional structures which exhibit their strongest chemical bonding in only two dimensions. In such materials, the stronger chemical bonds are formed in two-dimensional planes and a three-dimensional solid is formed by stacking such planes on top of each other. However, the interactions between the planes are weaker than the chemical bonds holding an individual plane together. The weaker bonds generally arise from interlayer attractions such as Van der Waals forces, electrostatic interactions, and hydrogen bonding. In those situations where the layered structure has electronically neutral sheets interacting with each other solely through Van der Waals forces, a high degree of lubricity is manifested as the planes slide across each other without encountering the energy barriers that arise with strong interlayer bonding. Graphite is an example of such a material. The silicate layers of a number of clay materials are held together by electrostatic attraction mediated by ions located between the layers. In addition, hydrogen bonding interactions can occur directly between complementary sites on adjacent layers, or can be mediated by interlamellar bridging molecules.
Laminated materials such as clays may be modified to increase their surface area. In particular, the distance between the layers can be increased substantially by absorption of various swelling agents such as water, ethylene glycol, amines, ketones, etc., which enter the interlamellar space and push the layers apart. However, the interlamellar spaces of such layered materials tend to collapse when the molecules occupying the space are removed by, for example, exposing the clays to high temperatures. Accordingly, such layered materials having enhanced surface area are not suited for use in chemical processes involving even moderately severe conditions.
The extent of interlayer separation can be estimated by using standard techniques such as X-ray diffraction to determine the basal spacing, also known as "repeat distance" or "d-spacing". These values indicate the distance between, for example, the uppermost margin of one layer with the uppermost margin of its adjoining layer. If the layer thickness is known, the interlayer spacing can be determined by subtracting the layer thickness from the basal spacing.
Various approaches have been taken to provide layered materials of enhanced interlayer distance having thermal stability. Most techniques rely upon the introduction of an inorganic "pillaring" agent between the layers of a layered material For example, U.S. Pat. No. 4,216,188 incorporated herein by reference discloses a clay which is cross-linked with metal hydroxide prepared from a highly dilute colloidal solution containing fully separated unit layers and a cross-linking agent comprising a colloidal metal hydroxide solution. However, this method requires a highly dilute forming solution of clay (less than 1 g/l) in order to effect full layer separation prior to incorporation of the pillaring species, as well as positively charged species of cross linking agents. U.S. Pat. No. 4,248,739, incorporated herein by reference, relates to stable pillared interlayered clay prepared from smectite clays reacted with cationic metal complexes of metals such as aluminum and zirconium. The resulting products exhibit high interlayer separation and thermal stability.
U.S. Pat. No. 4,176,090, incorporated herein by reference, discloses a clay composition interlayered with polymeric cationic hydroxy metal complexes of metals such as aluminum, zirconium and titanium. Interlayer distances of up to 16 A are claimed although only distances restricted to about 9 A are exemplified for calcined samples. These distances are essentially unvariable and related to the specific size of the hydroxy metal complex.
Silicon-containing materials are believed to be a highly desirable species of intercalating agents owing to their high thermal stability characteristics. U.S. Pat. No. 4,367,163, incorporated herein by reference, describes a clay intercalated with silica by impregnating a clay substrate with a silicon-containing reactant such as an ionic silicon complex, e.g., silicon acetylacetonate, or a neutral species such as SiCl.sub.4. The clay may be swelled prior to or during silicon impregnation with a suitable polar solvent such as methylene chloride, acetone, benzaldehyde, tri- or tetraalkylammonium ions, or dimethylsulfoxide. This method, however, appears to provide only a monolayer of intercalated silica resulting in a product of small spacing between layers, about 2-3 A as determined by X-ray diffraction.
U.S. Pat. No. 4,859,648 describes layered oxide products of high thermal stability and surface area which contain interlayer polymeric oxides such as polymeric silica. These products are prepared by ion exchanging a layered metal oxide, such as layered titanium oxide, with organic cation, to spread the layers apart. A compound such as tetraethylorthosilicate, capable of forming a polymeric oxide, is thereafter introduced between the layers. The resulting product is treated to form polymeric oxide, e.g., by hydrolysis, to produce the layered oxide product. The resulting product may be employed as a catalyst material in the conversion of hydrocarbons.
Crystalline oxides include both naturally occurring and synthetic materials. Examples of such materials include porous solids known as zeolites. The structures of crystalline oxide zeolites may be described as containing corner-sharing tetrahedra having a three-dimensional four-connected net with T-atoms at the vertices of the net and O-atoms near the midpoints of the connecting lines. Further characteristics of certain zeolites are described in Collection of Simulated XRD Powder Patterns for Zeolites by Roland von Ballmoos, Butterworth Scientific Limited, 1984.
Synthetic zeolites are often prepared from aqueous reaction mixtures comprising sources of appropriate oxides. Organic directing agents may also be included in the reaction mixture for the purpose of influencing the production of a zeolite having the desired structure. The use of such directing agents is discussed in an article by Lok et al. entitled "The Role of Organic Molecules in Molecular Sieve Synthesis" appearing in Zeolites, Vol. 3, October, 1983, pp. 282-291.
After the components of the reaction mixture are properly mixed with one another, the reaction mixture is subjected to appropriate crystallization conditions. Such conditions usually involve heating of the reaction mixture to an elevated temperature possibly with stirring. Room temperature aging of the reaction mixture is also desirable in some instances.
After the crystallization of the reaction mixture is complete, the crystalline product may be recovered from the remainder of the reaction mixture, especially the liquid contents thereof. Such recovery may involve filtering the crystals and washing these crystals with water. However, in order to remove all of the undesired residue of the reaction mixture from the crystals, it is often necessary to subject the crystals to a high temperature calcination e.g., at 500.degree. C., possibly in the presence of oxygen. Such a calcination treatment not only removes water from the crystals, but this treatment also serves to decompose and/or oxidize the residue of the organic directing agent which may be occluded in the pores of the crystals, possibly occupying ion exchange sites therein.
It has been discovered that a certain synthetic crystalline oxide undergoes a transformation during the synthesis thereof from an intermediate swellable layered state to a non-swellable final state having order in three dimensions, the layers being stacked upon one another in an orderly fashion. This transformation may occur during the drying of the recovered crystals, even at moderate temperatures, e.g., 110.degree. C. or greater. By interrupting the synthesis of these materials prior to final calcination and intercepting these materials in their swellable intermediate state, it is possible to interpose materials such as swelling, pillaring or propping agents between these layers before the material is transformed into a non-swellable state. When the swollen, non-pillared form of these materials is calcined, these materials may be transformed into materials which have disorder in the axis perpendicular to the planes of the layers, due to disordered stacking of the layers upon one another.
The hydrocracking of hydrocarbons to produce lower boiling hydrocarbons and, in particular, hydrocarbons boiling in the motor fuel range, is an operation upon which a vast amount of time and effort has been spent in view of its commercial significance. Hydrocracking catalysts usually comprise a hydrogenation-dehydrogenation component deposited on an acidic support such as silica-alumina, silica-magnesia, silica-zirconia, alumina, acid-treated clays, zeolites, and the like.
Zeolites have been found to be particularly effective in the catalytic hydrocracking of a gas oil to produce motor fuels, and such has been described in many U.S. patents including U.S. Pat. Nos. 3,140,249; 3,140,251; 3,140,252; 3,140,253; and 3,271,418.
A catalytic hydrocracking process utilizing a catalyst comprising a zeolite dispersed in a matrix of other components such as nickel, tungsten, and silica-alumina is described in U.S. Pat. No. 3,617,498.
A hydrocracking catalyst comprising a zeolite and a hydrogenation-dehydrogenation component such as nickel-tungsten sulfide is disclosed in U.S. Pat. No. 4,001,106.
The hydrocracking process described in U.S. Pat. No. 3,758,402 utilizes a catalyst possessing a large-pore size zeolite component such as zeolite X or Y and an intermediate-pore size zeolite component such as ZSM-5 with a hydrogenation-dehydrogenation component such as nickel-tungsten being associated with at least one of the zeolites.
Hydrocarbon conversion utilizing a catalyst comprising a zeolite, such as ZSM-5, having a zeolite particle diameter in the range of 0.005 micron to 0.1 micron and in some instances containing a hydrogenation-dehydrogenation component is disclosed in U.S. Pat. No. 3,926,782.
The hydrocracking of lube oil stocks employing a catalyst comprising a hydrogenation component and a zeolite such as ZSM-5 is disclosed in U.S. Pat. No. 3,755,145.
Hydrocracking operations featuring the use of dual reaction stages, or zones, and/or two different catalysts are also known.
U.S. Pat. No. 3,535,225 discloses a dual-catalyst hydrocracking process in which a hydrocarbon feedstock is initially contacted with a first catalyst comprising a hydrogenation component and a component selected from the group consisting of alumina and silica-alumina and subsequently with a second catalyst provided as a silica-based gel, a hydrogenation component and a zeolite in the ammonia or hydrogen form and free of any loading metal or metals.
U.S. Pat. No. 3,536,604 discloses a hydrofining-hydrocracking process in which a hydrocarbon feed containing 300 to 10,000 ppm organic nitrogen is contacted with a hydrofining catalyst comprising a Group VI or Group VIII metal on an alumina or silica-alumina support whereby the organic nitrogen content of the feed is reduced to a level of 10 ppm to 200 ppm, a substantial portion of the resulting hydrofined effluent thereafter being contacted with a second catalyst comprising a gel matrix comprising at least 15 wt. % silica, alumina, nickel and/or cobalt, molybdenum and/or tungsten, and a zeolite in the ammonia or hydrogen form and fee of any loading metal.
U.S. Pat. No. 3,536,605 discloses a hydrofining-hydrocracking process in which a hydrocarbon feed containing substantial amounts of organic nitrogen is contacted in a hydrofining reaction zone under hydrofining conditions with a catalyst comprising a gel matrix comprising silica and alumina and nickel and/or cobalt and molybdenum and/or tungsten and a zeolite having a silica-to-alumina ratio above about 2.15, a unit cell size below about 24.65 Angstroms (A), and a sodium content below about 3 wt. % to produce a hydrofined product of reduced nitrogen content. The effluent from the hydrofining reaction zone is then hydrocracked in a hydrocracking reaction zone under hydrocracking conditions in the presence of hydrogen and a hydrocracking catalyst.
U.S. Pat. No. 3,558,471 discloses a two-catalyst process wherein a hydrocarbon feedstock is first hydrotreated in the presence of a catalyst comprising a silica-alumina gel matrix containing nickel or cobalt, or both, and molybdenum or tungsten, or both, and a zeolite substantially in the ammonia or hydrogen form free of any catalytic loading metal or metals, the zeolite having a silica-to-alumina ratio above about 2.15, unit cell size below about 24.65 A, and a sodium content below about 3 wt. %, calculated as Na.sub.2 O, to produce a first effluent which is thereafter hydrocracked in a second reaction zone in the presence of a hydrocracking catalyst which may be the same catalyst used in the first reaction zone or a conventional hydrocracking catalyst.
U.S. Pat. No. 3,788,974 discloses a two-catalyst hydrocracking process wherein a hydrocarbon oil feedstock containing from about 0.01 to 0.5 wt. % nitrogen compounds is contacted in a first hydrocracking zone with a zeolite catalyst of the faujasite type in combination with a nickel/tungsten hydrogenation component to provide an effluent which is contacted in a second separate hydrocracking zone with a hydrocracking catalyst, preferably zeolite X or Y.
In U.S. Pat. Nos. 3,894,930 and 4,054,539, a hydrocracking process is disclosed which employs a catalyst comprising a hydrogenation component, an ultrastable zeolite and a silica-alumina cracking catalyst.
U.S. Pat. No. 4,612,108 discloses a process in which an initial hydrotreating stage employing a conventional hydrotreating catalyst is followed by a hydrocracking stage employing zeolite Beta as the hydrocracking catalyst.
Catalytic hydrocracking of a hydrocarbon feedstock can in certain cases be accompanied by dewaxing, that is selective conversion of straight-chain and slightly branched paraffins, such that the pour point of the product is reduced. See U.S. Pat. No. 3,668,113.
It is known to produce a high quality lube base stock oil by subjecting a waxy crude oil fraction to solvent refining, followed by catalytic dewaxing over ZSM-5, with subsequent hydrotreating of the lube base stock as described in U.S. Pat. No. 4,181,598. Zeolites such as ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, and ZSM-38 have been proposed for dewaxing processes and their use is described in U.S. Pat. Nos. 3,894,938; 4,176,050; 4,181,598; 4,222,855; 4,229,282; and 4,247,388. A dewaxing process employing synthetic offretite is described in U.S. Pat. No. 4,259,174.
The use of zeolite Beta as catalyst for dewaxing hydrocarbon feedstocks such as distillate fuel oils by isomerization is described in U.S. Pat. Nos. 4,419,220 and 4,501,926. U.S. Pat. No. 4,486,296 teaches hydrodewaxing and hydrocracking of a hydrocarbon feedstock over a three-component catalyst including zeolite Beta. Dewaxing a paraffin-containing hydrocarbon feedstock employing a hydrotreating step prior to the dewaxing step over zeolite Beta catalyst is disclosed in U.S. Pat. Nos. 4,518,485 and 4,612,108. U.S. Pat. No. 4,481,104 discloses distillate-selective hydrocracking using a large-pore, high silica, low acidity catalyst, e.g. zeolite Beta catalyst. Hydrocracking C.sub.5 + naphthas over a catalyst comprising zeolite Beta is disclosed in U.S. Pat. No. 3,923,641. A dewaxing process using a noble metal/zeolite Beta catalyst followed by a base metal/zeolite Beta catalyst is disclosed in U.S. Pat. No. 4,554,065. U.S. Pat. No. 4,541,919 discloses a dewaxing process using a large-pore zeolite catalyst such as zeolite Beta which has been selectively coked. U.S. Pat. No. 4,435,275 describes a moderate pressure hydrocracking process which may use a catalyst comprising zeolite Beta for producing low pour point distillates.
European patent application No. 94,827 discloses the use of zeolite Beta for hydrocracking and compares it for that process with other hydrocracking catalyst such as high silica zeolite Y, zeolite X, and ZSM-20 (as described in European patent application No. 98,040). U.S. Pat. No. 4,612,108 describes the hydrocracking and dewaxing of waxy petroleum fractions by passing the fractions over a hydrocracking catalyst comprising zeolite Beta and a matrix material in the presence of hydrogen and under hydrocracking conditions, the proportion of zeolite Beta in the hydrocracking catalyst increasing in the direction in which the fraction is passed.
U.S. Pat. No. 4,601,993 describes the dewaxing of a lubricating oil feedstock by passing the waxy fraction over a catalyst bed containing a mixture of medium-pore size zeolite and large-pore zeolite having a Constraint Index of less than 2 and having a hydroisomerization activity in the presence of a hydrogen component.
U.S. Pat. No. 4,358,362 discloses a dewaxing process in which the feed is subjected to pretreatment with a zeolite sorbent to sorb zeolite poisons present therein.
It is known to produce lubricating oil of improved properties by hydrotreating the lubricating oil base stock in the presence of ZSM-39 containing cobalt and molybdenum, as shown in U.S. Pat. No. 4,395,327.
U.S. Pat. Nos. 4,968,402; 5,000,839; and 5,013,422 describe various hydrocracking reactions conducted over catalysts comprising MCM-22.